Artificial cloning in plants

Micropropagation using tissue culture

• Micropropagation = process of making large numbers of genetically identical offspring from one parent plant using tissue culture techniques
• This is used when the desirable plant:
  • Doesn't readily produce seeds
  • Doesn't respond well to natural cloning
  • Is very rare
  • Has been genetically modified or selective bred with difficulty
  • Is required to be "pathogen-free" by growers
• One protocol uses sodium dichloroisocyanurate to keep the plants sterile without being in a sterile lab
• Basic principles of micropropagation and tissue culture are:
  1. Take a small sample of tissue from a plant - the meristem tissue from shoot tips if often dissected out in sterile conditions to prevent contamination
  2. The sample is sterilised, usually by being immersed in bleach or ethanol
  3. Material removed from the plant is called the explant
  4. The explant is placed in a sterile culture medium containing plant hormones which stimulate mitosis
  5. The cells divide, forming a mass of identical cells called a callus
  6. The callus is divided up and individual cells are transferred into a new culture medium containing a different mixture of plant hormones and nutrients to stimulate development of tiny plantlets
  7. The plantlets are potted out to grow and produce a crop

Arguments for micropropagation

• Allows for rapid production large numbers of plants with known genetic make-up
• Culturing meristem tissue produces disease-free plants
• Makes it possible to produce viable numbers of plants after genetic modification
• Way of producing large numbers of plants that are seedless and therefore sterile to consumer tastes
• Provides a way of producing plants that are usually infertile or difficult to grow from seed
• Reliable way of increasing numbers of rare plants

Arguments against micropropagation

• Produces a monoculture - susceptible to diseases
• Relatively expensive and requires skilled workers
• Explants and plantlets are vulnerable to infection
• If source material has a virus, all the new plants will too
• Large numbers of new plants are lost in the process